Nice post @bubke . I've got nothing against any creatures and wouldn’t kill anything just for being ugly - especially if it's basically harmless. Cockroaches are actually quite amazing and beautiful if you look at them a certain way, though I still don't really like to handle them. I think the reason people have a reaction of disgust (which is not the same as fear, which is what people feel when they see a spider or snake, for example) is that cockroaches live in dirty places - drains, bins etc.. It's one thing having them in your compost pile, another having them running all over your kitchen. Same as worms. Good to have loads of worms in your compost, bad to have one in the apple you're eating - but half a worm in your apple is even worse!
Disgust is indeed a much better word than fear, great contribution!
Ha, finding half a worm in your apple, that's where you start to understand the word disgust i guess :-)